Table 1.
Diversification rate and the appearance time for different classes
| Name | Size (no. of species) | Diversification rate γ (± SD) and origination rate ν (± SD) | Generations since origination | Estimated time to origination T (My) | Independent estimate of T (My) |
| Arachnida | 55,147 | γ = 0.055 ± 0.0064 | 144 (131–161) | 302 (183–450) | 420 |
| ν = 0.0359 ± 0.0023 | |||||
| Magnoliopsida (Angiospermopsida) | 87,281 | γ = 0.051 ± 0.0058 | 163 (148–182) | 342 (207–509) | 228 |
| ν = 0.015 ± 0.0012 | |||||
| Insecta | 661,370 | γ = 0.037 ± 0.0019 | 272 (260–285) | 571 (364–798) | 420 |
| ν = 0.0185 ± 0.0006 | |||||
| Diplopoda | 9,907 | γ = 0.23 ± 0.0348 | 32 (28–37) | 67 (39–103) | 420 |
| ν = 0.10 ± 0.012 | |||||
| Aves | 9,913 | γ = 0.08 ± 0.021 | 82 (67–107) | 172 (93–299) | 130 |
| ν = 0.089 ± 0.010 | |||||
| Passerine birds (order) | 6,198 | γ = 0.12 ± 0.015 | 54 (48–60) | 113 (67–168) | 82 |
| ν = 0.14 ± 0.013 | |||||
| Malacostraca | 18,419 | γ = 0.086 ± 0.0115 | 84 (76–95) | 176 (106–266) | 510 |
| ν = 0.068 ± 0.0054 | |||||
| Maxillopoda | 4,963 | γ = 0.06 ± 0.0096 | 94 (83–108) | 197 (116–302) | 500 |
| ν = 0.074 ± 0.0146 | |||||
| Amphibia | 5,753 | γ = 0.051 ± 0.0118 | 110 (93–137) | 231 (130–383) | 315 |
| ν = 0.032 ± 0.0042 | |||||
| Mammalia | 4,832 | γ = 0.15 ± 0.0176 | 42 (39–47) | 88 (54–131) | 120 |
| ν = 0.118 ± 0.019 |
The SGD of each class has been fitted (Fig. 2 shows an example) using the SEO model to yield the diversification rate γ (column 3). From the total number of species in the class (column 2) and the diversification rate, one may extract the number of generations since the first appearance of this class (column 4). To translate generations to time, we took a single generation (typical time to extinction) as 2.1 (1.4–2.8) My as presented in column 5. This result of the SEO model should be compared with other independent estimates based on either fossil data or genetic analysis (column 6). In most cases, the SEO-based estimates are close to the results from independent sources. Note that the definition of generation time is quite arbitrary and may vary among classes, which may explain some mismatch with the fossil data. The factor-of-two differences for Malacostraca and Maxillopoda may be related to incomplete data about the number of species. For Diplopoda, the estimates are inconsistent; they may reflect an inadequacy of our demographic model in this case or an underestimation for the generation time of diplopod species. The Mammal class is dominated by the placentals (4,600 of 4,832 species), and therefore, the appropriate time is given for the placentals. The references to independent estimates of T are given in SI Appendix, Table S3.